This French classic is made with prepared pastry dough as the base and top; pierce the bottom dough all over with the tines of a fork to keep it from puffing up during baking. The filling is a simple mixture of butter, sugar, eggs, and ground almonds (or almond flour or meal), with rum adding subtle flavor. Once the remaining pastry sheet is placed on top and the edges sealed to fully enclose, it's brushed with lightly beaten egg yolks to encourage browning.